In the past, sulfurized sperm oil was widely used as an additive in many lubricant formulations such as gear oil, including lubricants for worm and spur gears, automatic transmission fluids, metal-working lubricants and the like. Sulfurized sperm oil is especially useful for improving extreme pressure properties while providing excellent lubricity and some degree of rust-inhibition in motor oils, gear lubricants, and rolling oils. However, the sulfurized sperm oils have been replaced in recent years by other sulfurized compositions as a result of the reduction in availability of sperm oil and increased cost. Sulfurized olefins do not always exhibit the degree of lubricity which is necessary in many applications.
Habiby, in U.S. Pat. Nos. 3,926,822 and 3,953,347, describes a composition comprising a sulfurized mixture of a fatty acid ester of a mono- or polyhydric alcohol, a fatty acid and an aliphatic olefin. Newingham et al, in U.S. Pat. Nos. 3,825,495 and 4,180,466, teaches lubrication of controlled-slip differentials with a composition comprising a co-sulfurized blend of a triglyceride and a monoolefin. Recchuite, in a series of U.S. Pat. Nos., for example, patent numbers U.S. Pat. No. 4,166,796, U.S. Pat. No. 4,166,797, U.S. Pat. No. 4,321,153 and U.S. Pat. No. 4,456,540 teaches compositions comprising a co-sulfurized mixture of triglycerides and an olefinic hydrocarbon. The '540 patent also recites the presence of a fatty acid in the reaction mixture. In U.S. Pat. No. 4,166,795, Recchuite teaches the reaction product of sulfur, lard oil, polyisobutylene oligomers and optionally another unsaturated material. All of these patents describe the use of these sulfurized mixtures in lubricants. Other sulfurized fatty acid esters are described in Lincoln et al, U.S. Pat. No. 2,113,811; Wasson et al, U.S. Pat. No. 2,672,444; Eby, U.S. Pat. No. 2,680,718; Wakim, U.S. Pat. No. 3,986,966; Zipf, U.S. Pat. No. 4,036,769; Hotten, U.S. Pat. No. 4,053,427; and Jackisch, U.S. Pat. No. 4,176,072. The sulfurization described in the above-identified patents generally is carried out using elemental sulfur. Several patents describe alternative means of incorporating sulfur including reactions with sulfur monochloride and phosphosulfurization carried out by addition of small amounts of a phosphorus sulfide.